<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			/* 1.导航条，抓导航外围空间#nav */
			#nav{
				width: 100%;
				height: 100px;
				background: #005500;
			}
			/* 2.导航条，抓到内围空间.nav_left 设置左浮动
			 
			 */
			#nav .nav_left{
				float: left;
				width: 300px;
				height: 100px;
				background: red;
			}
			/* 3.导航条，抓到内围空间.nav_right 设置右浮动*/
			#nav .nav_right{
				float: right;
				width: 300px;
				height: 100px;
				background: #aa55ff;
			}
		</style>
	</head>
	<body>
		<!-- html结构 外层div,内层套俩 -->
		<div id="nav">
			<div class="nav_left">左侧内容</div>
			<div class="nav_right">右侧内容</div>
		</div>
	</body>
</html>